MRI of the human eye using magnetization transfer contrast enhancement

PURPOSE. To determine the feasibility of using magnetization transfer contr ast-enhanced magnetic resonance imaging (MRI) to track cataractous lens cha nges. METHODS. A fast spin-echo sequence was modified to include a magnetization transfer contrast (MTC) preparation pulse train. This consisted of twenty 8 .5-msec sine pulses, 1200 Hz upfield from the water resonance and 1.2-Hz po wer. The MTC preparation pulse was followed by acquisition through fast spi n-echo imaging. The imaging parameters were number of excitations (NEX) = 1 , echo time (TE) = 14 msec, recovery time (TR) = 2 sec, echo train length o f eight echos, and a matrix size of 256 x 160. To reduce motion artifacts, the volunteers were asked to fixate on a blinking LED. Normal and MTC-enhan ced images were acquired from normal volunteers and volunteers with nuclear or cortical cataracts. RESULTS. The eye was adequately imaged, with few motion artifacts appearing . The lens was well resolved, despite the short T-2. The cornea and ciliary body were also clearly visible. In the lens, resolution of the epithelium and cortex were enhanced with MTC. In addition, contrast-to-noise ratios we re measured for each image. Examination of the contrast-to-noise ratio conf irmed that MTC increased the contrast between the nucleus and cortex. Unenh anced MRIs showed significant differences between the cortex of normal volu nteers and volunteers with cataracts. MTC-enhanced images improved the sens itivity to changes in the nucleus. CONCLUSIONS. In this preliminary study, we were able to use MTC-enhanced MR I to obtain high-contrast images of the human lens. Regular and enhanced MR Is detected statistically significant differences between normal and catara ctous lenses.